U.S. patent number 6,850,771 [Application Number 10/179,677] was granted by the patent office on 2005-02-01 for uplink power control.
This patent grant is currently assigned to QUALCOMM Incorporated. Invention is credited to Tao Chen, Durga P. Malladi, Serge Willenegger.
United States Patent |
6,850,771 |
Malladi , et al. |
February 1, 2005 |
Uplink power control
Abstract
Uplink power control is provided to maintain the integrity of
the uplink HS-DPCCH when the UE goes into SHO. The target pilot SNR
threshold is controlled by considering the pilot signal strength of
the serving Node-B and/or the uplink channel condition of the
serving Node-B when deciding to increase or decrease the target
pilot SNR threshold of Nodes-B.
Inventors: |
Malladi; Durga P. (San Diego,
CA), Willenegger; Serge (Onnens, CH), Chen;
Tao (San Diego, CA) |
Assignee: |
QUALCOMM Incorporated (San
Diego, CA)
|
Family
ID: |
29999142 |
Appl.
No.: |
10/179,677 |
Filed: |
June 24, 2002 |
Current U.S.
Class: |
455/522; 370/318;
370/320; 455/437; 455/516 |
Current CPC
Class: |
H04W
52/12 (20130101); H04W 52/24 (20130101); H04W
52/241 (20130101); H04W 52/286 (20130101); H04W
52/225 (20130101); H04W 52/146 (20130101); H04W
52/20 (20130101); H04W 52/40 (20130101) |
Current International
Class: |
H04B
7/005 (20060101); H04B 007/00 (); H04Q
007/20 () |
Field of
Search: |
;455/522,516,422.1,442,436,437,13.4 ;370/318,320,331,333,335 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1067706 |
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Jan 2001 |
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EP |
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1164714 |
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Dec 2001 |
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EP |
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1248388 |
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Oct 2002 |
|
EP |
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WO 01/11800 |
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Feb 2001 |
|
WO |
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WO 01/95521 |
|
Dec 2001 |
|
WO |
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WO 02/080400 |
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Oct 2002 |
|
WO |
|
Other References
Blaise et al, "Power control algorithms for soft handoff users in
UMTS", Motorola Labs, CRM Paris. Jun. 27, 2002.* .
NEC and Telecom Modus, "A method utilizing DL reference power to
avoid power drifting", Sophia Antipolis, France, Sep. 20, 1999.*
.
Sony Corporation, "Reduction of DL channel quality feedback rate
for HSDPA", Las Vegas, NV, Feb. 27, 2001..
|
Primary Examiner: Corsaro; Nick
Assistant Examiner: Orgad; Edan
Attorney, Agent or Firm: Wadsworth; Philip Nguyen; Thien T.
Kordich; Donald C.
Claims
What is claimed is:
1. An apparatus for uplink power control, comprising: determination
logic for determining a channel condition of an uplink channel; and
a target pilot signal-to-noise (SNR) threshold setter for
increasing a target pilot SNR threshold when the determined channel
condition is unsatisfactory, wherein the determined channel
condition is unsatisfactory when the average SNR of a pilot signal
is less than a predetermined first threshold and an average block
error rate over the uplink channel is greater than a predetermined
second threshold.
2. The apparatus of claim 1, further comprising a traffic-to-pilot
ratio setter for reducing the traffic-to-pilot ratio when the
target pilot SNR threshold is increased.
3. The apparatus of claim 1, wherein the target pilot
signal-to-noise (SNR) threshold setter decreases the target pilot
SNR threshold when the determined channel condition is
satisfactory.
4. The apparatus of claim 1, wherein the determined channel
condition is unsatisfactory when the average SNR of a pilot signal
is less than a predetermined first threshold.
5. The apparatus of claim 1, wherein the determined channel
condition is unsatisfactory when the average block error rate over
an uplink data channel is greater than a predetermined second
threshold.
6. An apparatus for uplink power control comprising: a
signal-to-noise (SNR) averager for computing the average SNR or an
uplink pilot signal; a block-error-rate (BLER) averager for
computing the average BLER or an uplink data signal; determination
logic for determining the channel condition of an uplink channel is
satisfactory or unsatisfactory according to the average SNR or
average BLER or both; and a target pilot signal-to-noise (SNR)
threshold setter for increasing a target pilot SNR threshold when
the determined channel condition is unsatisfactory and for
decreasing the target pilot SNR threshold when the determined
channel condition is satisfactory.
7. A method for uplink power control, comprising: determining a
channel condition of an uplink channel; and increasing a target
pilot SNR threshold when the determined channel condition is
unsatisfactory, wherein the determined channel condition is
unsatisfactory when the average SNR of a pilot signal is less than
a predetermined first threshold and an average block error rate
over the uplink channel is greater than a predetermined second
threshold.
8. The method of claim 7 further comprising reducing a
traffic-to-pilot ratio when the target pilot SNR threshold is
increased.
9. The method of claim 7 further comprising decreasing the target
pilot SNR threshold when the determined channel condition is
satisfactory.
10. The method of claim 7 wherein the determined channel condition
is unsatisfactory when the average SNR of a pilot signal is less
than a predetermined first threshold.
11. The method of claim 7 wherein the determined channel condition
is unsatisfactory when the average block error rate over an uplink
data channel is greater than a predetermined second threshold.
12. A method for uplink power control comprising: computing the
average SNR or an uplink pilot signal; computing the average BLER
or an uplink data signal; determining whether the channel condition
of an uplink channel is satisfactory or unsatisfactory according to
the average SNR or average BLER or both; and increasing a target
pilot SNR threshold when the determined channel condition is
unsatisfactory and for decreasing the target pilot SNR threshold
when the determined channel condition is satisfactory.
13. An apparatus for uplink power control comprising: means for
determining a channel condition of an uplink channel; and means for
increasing a target pilot SNR threshold when the determined channel
condition is unsatisfactory, wherein the determined channel
condition is unsatisfactory when the average SNR of a pilot signal
is less than a predetermined first threshold and an average block
error rate over the uplink channel is greater than a predetermined
second threshold.
14. The apparatus of claim 13 further comprising reducing a
traffic-to-pilot ratio when the target pilot SNR threshold is
increased.
15. The apparatus of claim 13 further comprising decreasing the
target pilot SNR threshold when the determined channel condition is
satisfactory.
16. The apparatus of claim 13 wherein the determined channel
condition is unsatisfactory when the average SNR of a pilot signal
is less than a predetermined first threshold.
17. The apparatus of claim 13 wherein the determined channel
condition is unsatisfactory when the average block error rate over
an uplink data channel is greater than a predetermined second
threshold.
18. An apparatus for uplink power control comprising: means for
computing the average SNR or an uplink pilot signal; means for
computing the average BLER or an uplink data signal; means for
determining whether the channel condition of an uplink channel is
satisfactory or unsatisfactory according to the average SNR or
average BLER or both; and means for increasing a target pilot SNR
threshold when the determined channel condition is unsatisfactory
and for decreasing the target pilot SNR threshold when the
determined channel condition is satisfactory.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of wireless
communication, and, more specifically, to uplink power control.
Although the present invention is subject to a wide range of
applications, it is especially suited for use in a cellular
communication system, and will be described in that connection.
2. Description of the Related Art
Technical Specification 3GPP TS 25.211 v5.0.0 (2002-03), 3rd
Generation Partnership Project (3GPP); Technical Specification
Group Radio Access Network; Physical channels and mapping of
transportation channels onto physical channels (FDD) (Release 5)
provides for a High Speed Downlink Shared Channel (HS-DSCH). The
HS-DSCH is a downlink transport channel shared by one or several
user equipment (UE).
In 3GPP High Speed Data Packet Access (HSDPA), a UE can be in soft
handoff (SHO) with multiple Node-Bs for the Dedicated Physical
Channel (DPCH) on downlink. There is, however, no HSDPA SHO for the
High Speed Downlink Shared Channel (HS-DSCH) and corresponding
uplink High Speed Dedicated Physical Control Channel (HS-DPCCH).
This may result in a condition called link imbalance. That is, the
Node-B serving the high speed data over the HS-DSCH is different
from the Node-B to which the UE has the best uplink for the
DPCCH.
A need therefore exists for apparatus and methods for uplink power
control during link imbalance that considers the reverse link
HS-DPCH.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the present invention will be set
forth in part in the description which follows and accompanying
drawings, wherein the preferred embodiments of the present
invention are described and shown, and in part become apparent to
those skilled in the art upon examination of the following detailed
description taken in conjunction with the accompanying drawings, or
may be learned by practice of the present invention. The advantages
of the present invention may be realized and attained by means of
the instrumentalities and combinations particularly pointed out in
the appended claims.
FIG. 1 is a generalized block diagram of a communication system
configured according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates a generalized block diagram of a communication
system 100. User equipment (UE) 102 can be in wireless
communication with a Node-B1104 and a Node-B2106. The UE can be a
device, such as, a cellular phone or other fixed or mobile wireless
devices. A Node-B can be a device, such as, a cellular base station
that serves an entire cell.
Node-B1104 and Node-B2106 can be in communication with Radio
Network Controller (RNC) 108. The RNC receives signals from Node
B-1 and Node-B2 and provides control information, among other
things, to Node-B1 and Node-B2.
UE 102 can be in the coverage area of Node-B1104 and Node-B2106,
and can communicate with Node-B1 and Node-B2 over various channels.
For example, the Nodes-B can communicate signals to the UE over
downlink channels, for example, downlink Dedicated Physical Channel
(DPCH) denoted as Dedicated Physical Data Channel (DPDCH) and
Dedicated Physical Control Channel (DPCCH) in FIG. 1, and High
Speed Downlink Shared Channel (HS-DSCH). The UE can send signals to
the Nodes-B over uplink channels, such as, uplink DPDCH, uplink
DPCCH, and High Speed Dedicated Physical Control Channel (HS-DPCCH)
associated with downlink HS-DSCH.
UE 102 can send an omnidirectional pilot signal comprising blocks
of data over uplink DPCCH, in addition to feedback information bits
(FBI) and UP/DOWN request signals for the downlink power
control.
The UE's pilot signal can be received by Nodes-B within range of
the pilot signal. Each Node-B has a target pilot signal-to-noise
(SNR) threshold T at which it desires to receive the pilot signal
from the UE. Each Node-B receiving the pilot signal can calculate
the SNR of the received pilot signal. (Blocks 110 and 112.) If the
calculated SNR is below the threshold T, a Node-B can request the
UE to increase the transmit power of the pilot signal by sending an
UP request over DPCCH. (Blocks 114 and 116.) If the calculated SNR
is above the threshold T, a Node-B can request the UE to decrease
the transmit power of the pilot signal by sending a DOWN request
over DPCCH. (Blocks 118 and 120.)
An OR of DOWNs determines whether to increase or decrease the pilot
signal strength. If the UE receives a DOWN request from any one of
the Nodes-B, then the UE's pilot strength is decreased. If the UE
receives UP requests from all of the Nodes-B, then the UE's pilot
strength is increased.
A link imbalance may occur when UE 102 is receiving high speed data
from Node-B1 over channel HS-DSCH and is in an uplink SHO state
with Node-B1 and Node-B2. This link imbalance condition can occur
when Node-B2 is sending a DOWN request and Node-B1 is sending an UP
request. In addition, the UE can vary its transmit power according
to the conventional OR of DOWNs when in SHO state.
The reduction of pilot signal transmit power by UE 102 can affect
the uplink high speed communications between the UE and Node-B1104
because the signal strength of HS-DPCCH will be reduced in
proportion to the reduction of the pilot signal strength in
accordance with a traffic-to-pilot ratio stored in the UE.
In HSDPA, Node-B1104 can send packet data to UE 102 over HS-DSCH.
The UE can only receive packet data from one Node-B at a time over
HS-DSCH. In FIG. 1, Node-B1104 is the Node transmitting packet date
to UE. Cell switching can occur that switches the UE from receiving
packet data from Node-B1 to receiving packet data from Node-B2106
over the downlink channel HS-DSCH associated with Node-B2 (not
shown). Higher level signaling achieves cell switching. Link
imbalance, however, can exist over a shorter time scale than that
of cell switching.
UE 102 can send an acknowledge/not-acknowledge (ACK/NAK) signal
over HS-DPCCH. An ACK is sent by the UE if the UE has successfully
received the packet data from the serving Node-B1 over HS-DSCH.
Conversely, a NAK is sent by the UE if the UE has unsuccessfully
received the packet data from the serving Node-B1 over HS-DSCH. If
a NAK is received by the sending Node-B1, the sending Node-B1 can
re-transmit the previously sent packet data. The UE can send
nothing (NULL) if it missed a High Speed Shared Control Channel
(HS-SCCH) associated with HS-DSCH. HS-SCCH indicates to the UE that
a future transmission is imminent on HS-DSCH.
In a link imbalance condition, Node-B2 transmits a DOWN request.
This causes UE 102 to decrease its pilot signal strength, and,
correspondingly, the signal strength of ACK/NAK. The decreased
strength of the ACK/NAK signal can result in ACKs being received as
NAKs that lead to increased transmissions on HS-DSCH; and NAKs or
NULLs being received as ACKs that lead to missed packets on
HS-DSCH.
Further, because the UE sends channel quality indication (CQI) over
HS-DPCCH, Node-B1 may receive false indications.
A solution to this problem is for the RNC 108 to monitor the pilot
strength, for example, the average SNR of the pilot signal received
by Node-B1104 (block 122) and the average block error rate (BLER)
of the serving Node-B1 (block 124). These parameters may be used in
determining whether to increase or decrease the target pilot SNR
threshold T.
The RNC 108 can compute the cyclic redundancy check of blocks
transmitted over uplink DPDCH for both Nodes-B (blocks 126 and
128). If the CRC fails for both channels (block 130), the RNC
directs the Nodes-B to increase the target pilot SNR threshold T
(block 132). This in turn makes it likely that Node-B2 will change
its request from a DOWN to an UP.
If the CRC does not fail for both channels (block 130), RNC 108
determines if the uplink channel condition between Node-B1104
transmitting the high speed packet data and the UE 102 is
unsatisfactory (block 134), for example, determining if the average
pilot signal SNR is less than a predetermined threshold TH1, or
determining if the block error rate (BLER) over DPDCH is greater
than a predetermined threshold TH2, or both. If the uplink channel
condition is satisfactory, then RNC 108 can request that the target
pilot SNR threshold T of the Nodes-B be decreased. (Block 136.)
If the uplink channel condition between Node-B1104 transmitting the
high speed packet data and the UE 102 is unsatisfactory (block
134), the RNC 108 can request that the target pilot SNR threshold T
be increased (block 138). The increased T makes it more likely that
Node-B2 will change its DOWN request to an UP request, which in
turn can prevent a decrease in the pilot strength of the UE
according to the OR of DOWNs.
Optionally, the RNC can request the the traffic-to-pilot ratio of
the Nodes-B be reduced (block 140) in addition to increasing T
(block 138). Reducing the traffic-to-pilot ratio reduces the
average return link interferences by reducing the traffic channel
strength in relation to the pilot signal strength.
The present invention is capable of other and different
embodiments, and its several details are capable of modification.
For example, although the invention is described with reference to
the aforementioned technical specification for Wideband Code
Division Multiple Access (W-CDMA), the invention can equivalently
be applied to CDMA2000 1xEV-DV. For example, the following 3GPP
terms have correspondence to CDMA2000 terms: UE corresponds to a
Mobile Station (MS); a Node-B corresponds to a Base Terminal
Station (BTS); RNC corresponds to a Base Station Controller (BSC);
HS-DSCH corresponds to Forward Packet Data Channel (F-PDCH); DPCH
corresponds to Fundicated Channel (FCH/DCCH); HS-DPCCH corresponds
to R-CQICH and R-ACKCH; and BLER corresponds to frame error rate
(FER).
Node-B can be a device a cellular base station having beam-forming
antennas that that serves various sectors of a cell. In this case,
the functions of the RNC can be performed in the base station
serving the UE for a link imbalance between sectors of the same
base station.
The functionality described herein, and of the blocks shown in FIG.
1, may be carried out in dedicated hardware, or equivalently, in
software and a processor.
In conclusion, the uplink power control described herein provides
the advantage to maintain the integrity of the uplink HS-DPCCH when
the UE goes into SHO. This is primarily accomplished by controlling
the target pilot SNR threshold by considering the pilot signal
strength of the serving Node-B1 and/or the uplink channel condition
the serving Node-B1 when deciding to increase or decrease the
target pilot SNR threshold of Nodes-B.
Those skilled in the art will recognize that other modifications
and variations can be made in the uplink power control technique of
the present invention and in construction and operation without
departing from the scope or spirit of this invention.
* * * * *